1. Field of the Invention
The present invention relates to a flow meter capable of detecting the flow rate of a fluid.
2. Description of the Related Art
A flow meter has been widely used, in which a flow velocity sensor is arranged within a fluid flow passage (piping) for a gas, for example, in order to measure the flow rate of the gas that flows through the flow passage using the flow velocity sensor.
The flow meter comprises, for example, a detecting section for rectifying and sensing the gas, a signal processing section for processing a signal derived from the detecting section, and a display section. A subminiature flow sensor is attached to an inner wall surface of a flow passage of the detecting section, which serves as the flow velocity sensor. The signal processing section calculates a cumulative flow rate and an instantaneous flow rate, on the basis of a detection signal fed from the flow sensor, wherein the obtained result is displayed on the display section.
In this arrangement, a plurality of wire meshes are arranged at constant intervals on an upstream side of the flow velocity sensor, which function as rectifying elements for suppressing uneven flow disturbances in the gas that flows through the flow passage. For example, Japanese Laid-Open Patent Publication No. 2004-93170 discloses an arrangement in which a fine metal mesh is arranged at an uppermost stream position of the flow velocity sensor, and a plurality of other metal meshes, having gradually coarser mesh sizes, are arranged with the finest mesh positioned at the downstream side, while the meshes are separated from each other by predetermined distances.
However, the technical concept disclosed in Japanese Laid-Open Patent Publication No. 2004-93170 requires that a plurality of spacers and metal meshes be alternately installed, respectively, along the inner wall surface of the flow passage in the fluid flow direction. Therefore, the assembly operation is complicated. Further, in the industrial field to which the invention pertains, an increase in the rectifying effect has been sought.